DE102016115028A1 - Nozzle head for spray nozzles for plastic injection molding machines - Google Patents

Abstract

Injection head (10) for injection nozzles (3) of plastic injection molding machines, comprising an inner tubular body or tip (11) and a ring nut (9). The tip (11) comprises a radially inner member (12) made of a first material, and a radially outer member (13) made of a second material attached in contact with the radially inner member (12) at a middle part (Fig. 16) of this element, terminating at a distance from its distal end (15). The ring nut (9) completely covers the radially outer element (13) and insulates it against the environment.

Description

Subject of the invention

The present invention relates to spray nozzles for plastic injection molding machines in general. In particular, the invention relates to a nozzle head for spray nozzles adapted to comprise an inner tubular body or tip defining a flow channel for the injected plastic material and a ring nut externally and coaxially secured to the tip.

State of the art

Nozzle heads of this type are known for example from the documents US 5299928 . US 6988883 and WO-2006/123237 , Typically, the inner tubular body or tip is made of a material of high thermal conductivity while the outer ring nut, which is intended to come into contact with a cooled in-use mold, is made of a material of low thermal conductivity to prevent heat loss to reduce.

The need to ensure the high thermal conductivity of the tip limits the choice of candidate material types in terms of composition, such as, e.g. Copper and its alloys, which may otherwise have low abrasion resistance and chemical resistance to the materials of the plastics through which they flow during the injection process.

In document US 7182591 Also disclosed is a nozzle head of the type defined above, the tip of which is made of two axial parts which are brazed together and correspond respectively to the proximal and distal ends of the tip. Both parts are made of the same material with high thermal conductivity, thus not even this design is able to solve the technical problem described above.

The documents EP-0755766A1 . FR-3012992A1 and US 2013 / 306686A1 disclose die heads without a ring nut in which the tip is formed by a body of high-resistance material having an annular space in which an insert of material of high thermal conductivity is arranged.

In document US 2009/148550 a nozzle head is described, which corresponds to the description before the characterizing part of claim 1, the tip of a radially inner member made of a first material with high durability, for example steel, and a radially outer member or sleeve, made of a second material having high thermal conductivity, for example copper, arranged to contact a substantial axial portion of the radially inner member to its distal end. The radially inner and the radially outer elements of the tip are interconnected by different systems, but none of them is capable of providing a stable mutual attachment - both axial and angular - and at the same time easy disassembly for maintenance purposes. In addition, the sleeve made of the high thermal conductivity material is partially exposed outside the tip and, during use, is subject to the risks associated with the penetration of plastic material and corrosion from the gases formed during casting, which can jeopardize the proper operation of the tip as a whole ,

Summary of the invention

The purpose of the present invention is to provide an effective and functional solution to the problem described above. This object is achieved thanks to a nozzle head of the type defined above, the main feature of which is that the radially outer element of the tip is attached to a middle part of the radially inner element which terminates at a distance from the distal end of the inner element and towards the ring nut exposed.

According to a first advantageous embodiment, the ring nut is designed as a "lead-through" and completely covers the radially outer element of the tip and thus insulates it against the environment, and the distal end of the radially inner element of the tip extends to the corresponding distal end of the ring nut.

Because of this solution, the radially outer member of the tip is effectively shielded against the surrounding corrosive environment during use and protected from it.

In one variant, the ring nut is designed as "outboard", i. it does not reach the distal end of the tip. In this case, apart from the advantage resulting from the reduction in the size of the sprue mark on the molded part in use, the seal with respect to the tool gate is restricted to only two elements, the tip and the mold plate.

Both embodiments ("feedthrough" and "outboard") allow for the achievement of significant functional advantages in terms of improvement in color changes of the plastic material due to less stagnation of the material and an improved temperature profile due to higher temperatures near the tool gate.

The radially outer element of the tip is advantageously mechanically connected to the radially inner element.

Thanks to this solution idea, the radially outer element of the tip is isolated against the flow of plastic material and against the gases generated during casting and so effectively protected, thereby avoiding the risk of tip malfunction.

In addition, for the radially inner and the radially outer members, the most suitable material, and a combination thereof, may be selected depending on the characteristics of the plastic material to be molded, the type of shape, and the design of the nozzle head.

With the aim of increasing the efficiency of the heat conduction, the connection of the radially inner element, radially outer element and ring nut is conveniently effected by intermeshing, which also reduces the risk that the radially outer element will detach from the radially inner element during maintenance work on the spray nozzle, For example, after removing the ring nut.

Brief description of the drawings

The invention will now be described in detail with reference to the drawings, purely by way of non-limiting example, wherein:

1 is a schematic representation and partial section in the vertical direction of an injection molding machine, which is equipped for example with two spray nozzles with nozzle heads in conventional or inventive design,

2 is a partial view on a larger scale of the conventional nozzle head,

3 a view analogous to 2 is that illustrates the first embodiment of the nozzle head according to the invention,

4 a view analogous to 3 is that the assembly consists of tip and ring nut of the nozzles 3 shows separately

5 and 6 enlarged details of 4 demonstrate,

7 an exploded view on a small scale of the assembly of tip and ring nut in 4 is and

8th and 9 Views analog 3 and 4 are, which represent a second embodiment of the nozzle head according to the invention.

Detailed description of the invention:

Originally, an injection molding machine of conventional design comprises with reference to FIG 1 a warm chamber 1 to which the pressurized plastic material to be cast in the liquid state in the example shown by the spray nozzles 2 . 3 - In the present case designed as needle valves - is supplied. Still in conventional design, each of the spray nozzles covers 2 . 3 a nozzle body 4 who with the warm chamber 1 communicates with and along a needle valve 5 controlled by a fluid or an electric actuator 6 , is axially movable.

The lower end of the needle valve 5 interacts with a nozzle head treated below to open or close the flow of plastic material to the injection port ("tool gate") of a mold.

The spray nozzle 2 is equipped with a conventional, the prior art, nozzle head and is denoted by reference numerals 7 designated and in 2 shown in more detail. It comprises an inner tubular body 8th , referred to as a tip and made of a single piece of a material with high thermal conductivity (usually copper or its alloys) and a hollow element 9 made of a material with lower thermal conductivity, referred to as a ring nut. The ring nut 9 is under the apex in an arrangement called the "lead-in" ring 8th at its free end to produce a sealed connection with a mold on the corresponding injection channel, ie the ring nut 9 reaches into the figure of the form.

The spray nozzle 3 that in the right part of 1 is instead equipped with a nozzle head according to the first embodiment of the invention and a total of 10 designated and in 3 to 7 shown in more detail. Also in this case it includes the ring nut 9 embodied as a "feedthrough" and substantially analogous to that of the prior art, as well as having an inner tubular body or tip referred to 11 Deviating therefrom is formed by two separate, ie separate and arranged in a certain manner assemblies. The first assembly consists of a radially inner element 12 made of a first material, and the second element consists of a radially outer element or sleeve 13 made of a second material, which is usually other than the first material.

The radially inner element 12 has a proximal end 14 , inserted and locked in the nozzle 4 , and a distal end 15 that extends from the nozzle and with the lower end of the needle valve 5 interacts. It narrows in from the proximal end 14 to the distal end 15 that is axial to the corresponding end of the ring nut 9 , marked with 9a , enough, and essentially flush with it.

The parts of the radially inner element 12 that is the proximal end 14 and the distal end 15 correspond, usually have a greater thickness, while the intermediate piece preferably has a smaller thickness and an outer annular recess 16 defined at a distance from the distal end 15 ends and the ring nut 9 is exposed. The radially outer element 13 is absorbed by this recess and rests in it. It should be noted that such a recess is not necessarily required, provided that it is only necessary that the radially outer element 13 in a middle part of the radially inner element 12 , the ring nut 9 is exposed, is to arrange.

As a result, the radially outer element surrounds 13 and coaxially surrounds the substantially central portion of the radially inner member 12 which extends below its proximal end 14 and over the distal end 15 this element is located. As a result, while the radially inner element 12 in contact with the plastic material flowing into the mold during casting, the radially outer element 13 but never comes in contact with the material. This allows the two elements 12 and 13 made of different materials, depending on the characteristics of the plastic material to be cast, the nature of the tool gate and the design of the nozzle head 11 can be selected as a needle valve as shown in the example or as a free-stream or torpedo flow valve and combined with each other.

As a result, the radially inner element becomes 12 required to protect against wear and oxidation caused by the plastic material, must be made of a first material having high mechanical strength, high abrasion resistance and high chemical resistance. Such a first material may consist of a hardened stainless steel, but with a very low thermal conductivity (16 W / mK) or also of a hardened stainless steel with a higher resistance to wear and a higher thermal conductivity (32 W / mK) or of tungsten, the offers an even higher conductivity - in the range around 80 W / mK - and has a hardness of 49 to 51 HRC.

The radially outer element 13 however, is made from a second material that can be chosen from a wide range: low thermal conductivity, such as titanium (4 W / mK) or higher conductivity, such as steel (16-36 W / mK) tungsten (80 W) / mK), copper and nickel alloys (60-140 W / mK), molybdenum alloys such as TZM (120 W / mK). However, the radially outer element becomes 13 preferably made of a material with high thermal conductivity such as copper or alloys of copper and beryllium (120-300 W / mK), aluminum (260 W / mK), electrolysis copper (300-390 W / mK) and even graphite (60 -400 W / mK).

As noted above, the selection and combination of the first and second materials is dependent upon the type of plastic material to be cast and the design of the gate. With regard to the characteristics of the plastic material, for example, crystalline material usually has the disadvantage of the so-called "cold grafting", ie cooling at the injection point, whereby the casting can be hindered or the temperature must be increased in order to continue the casting can. As a result, crystalline materials typically require a higher tip temperature 11 and thus is for the radially outer element 13 To prefer a material with very high conductivity.

An amorphous plastic material often behaves differently depending on the nature of the tip or tool gate design. For example, in the case of a nozzle with valve, these amorphous materials require a high temperature to achieve better flowability and thus avoid burring, especially when injecting directly into the figure, while in the free stream the temperature of the tip must be low in order to avoid problems "Threading" (formation of a plastic thread which is formed between the molded part and the nozzle when the part is opened and which is difficult to completely remove and may remain in the mold in subsequent casting operations) or "drooling" from the tool gate ( that is, the dripping of plastic material, which leads to aesthetic defects on the molded parts near the gate, or even makes casting impossible when the drop cools to close the tool gate).

The semi-crystalline plastic materials typically exhibit behavior between these two forms.

The design of the ring nut 9 of the nozzle head 10 can thus influence the behavior of the plastic material at the tool gate: For example, a "feed-through end ring" as shown in the figure as in the case of the previously described example may result in a hotter tool gate compared to an outer ring nut ("blind seat") as described below, in the latter case Mold pending tool cutting is usually colder. The radially outer element 13 has at least partial contact with the radially inner element 12 and the mutual coupling of both is achieved both by intermeshing and by mechanical adherence to, for example, the in 4 - 7 explained in more detail manner. The annular recess 16 is limited - on the side of the distal end 15 of the inner element 12 - By an annular cuff 17 and has - on the opposite side - one or more projections 18 for receiving the corresponding internal cavities 19 of the radially outer element 13 , Obviously, the arrangement of the projections 18 and cavities 19 also be the other way around.

The ring nut 9 that are different from the top 11 is distinguished and separated from this, is usually made of material with low conductivity and consequently stronger insulating effect such as titanium or steel with a hardness in the range 46-48 HRC, is coaxial at the top 11 attached so that they are the radially outer element 13 surrounding and completely covered so that it isolates the element from the environment and protects it from corrosive gases that form during injection of the plastic material. Advantageously, the ring nut 9 at least partially with the radially inner element 12 coupled and at least partially with the radially outer element 13 the top 11 coupled. Preferably, the ring nut 9 by meshing with correspondingly above and below the recess 17 located parts of the radially inner element 12 coupled and preferably it is also with the radially outer element 13 coupled by meshing.

8th and 9 in which the parts identical or similar to the parts described above are designated by the same reference numerals, show a second embodiment of the nozzle head 10 according to the invention, in which the ring nut, designated with 9 ' , executed as "outboard" instead of "execution". In this case, the ring nut ends 9 ' considerably before the distal end 15 of the radially inner element 12 and covers only part of the latter and its distal end 9 ' is located in a seat S of the plate P of the form. The distal end 15 of the radially inner element 12 the top 11 extends through a hole H of the plate P of the shape, which has a much smaller diameter than in the case of the "grommet" with the advantage that the sprue mark on the cast parts will be much smaller, which improves their aesthetic quality. In addition, also the sealing between the nozzle head 10 and the injection channel (tool cutting) of the mold in this case simplified, in that it is on the distal end 15 of the radially inner element inserted in hole H. 12 is limited. Even in this case, as in the case of the "performing" ring nut described above 9 , is the outer ring nut 9 ' at least partially with the radially inner element 12 coupled and at least partially with the radially outer element 13 coupled.

Obviously, the details of construction and embodiments may vary widely from what has been described and illustrated without departing from the scope of the present invention as described in the following claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5299928 [0002]
• US 6988883 [0002]
• WO 2006/123237 [0002]
• US 7182591 [0004]
• EP 0755766 A1 [0005]
• FR 3012992 A1 [0005]
• US 2013/306686 Al [0005]
• US 2009/148550 [0006]

Claims (15)

Nozzle head ( 10 ) for spray nozzles ( 3 ) of plastic injection molding machines, comprising an inner tubular body or a tip ( 11 ), which define a flow channel for the injected plastic material, and a ring nut ( 9 ; 9 ' ), which are outside and coaxial at the top ( 11 ), wherein the tip ( 11 ) a radially inner made of a first material and a proximal end ( 14 ) and a distal end ( 15 ) element ( 12 ), and a radially inner member made of a second material and mounted to engage with the radially inner member (10). 12 ) And in which the ring nut ( 9 ; 9 ' ) from the top ( 11 ) and the radially outer element ( 13 ) the top ( 11 ) from the radially inner element ( 12 ), characterized in that the radially outer element ( 13 ) the top ( 11 ) at a middle part ( 16 ) of the radially inner element ( 12 ), which is at a distance from the distal end ( 15 ) of this element ends and the ring nut ( 9 ; 9 ' ) is exposed. Nozzle head according to claim 1, characterized in that the ring nut ( 9 ) the radially outer element ( 13 ) completely covered and isolated against its environment. Nozzle head according to claim 2, characterized in that the distal end ( 15 ) of the radially inner element ( 12 ) to the corresponding distal end ( 9a ) said ring nut ( 9 ) enough. Nozzle head according to claim 1, characterized in that the ring nut ( 9 ' ) the radially outer element ( 13 ) only partially covered. Nozzle head according to claim 1, characterized in that the radially outer element ( 13 ) the top ( 11 ) in a peripheral annular recess of the radially inner element ( 12 ) is mounted and coupled with this. Nozzle head according to claim 5, characterized in that the recess ( 16 ) on the side of the distal end ( 15 ) of the radially inner element ( 12 ) by a radial annular sleeve ( 17 ) is limited and - on the opposite side - at least one projection ( 18 ) for the engagement of the radially outer element ( 13 ) having. Nozzle head according to one of the preceding claims, characterized in that the radially inner and the radially outer element ( 12 . 13 ) are coupled together by meshing. Nozzle head according to one of the preceding claims, characterized in that the ring nut ( 9 ; 9 ' ) by engagement with the radially inner element ( 12 ) is coupled. Nozzle head according to one of the preceding claims, characterized in that the ring nut ( 9 ; 9 ' ) by engagement with the radially outer element ( 13 ) is coupled. Nozzle head according to one of the preceding claims, characterized in that the first material has a high mechanical resistance, high abrasion resistance and high chemical resistance. Nozzle head according to claim 10, characterized in that the first material of hardened stainless steels, a non-stainless steel and tungsten is selected. Nozzle head according to one or more of the preceding claims, characterized in that the second material is selected from material with low or high thermal conductivity. Nozzle head according to claim 11, characterized in that the second material of titanium, steel, copper, copper beryllium alloys, copper-nickel alloys, aluminum and graphite is selected. Nozzle head according to one of the preceding claims, characterized in that the ring nut ( 9 ; 9 ' ) at least partially with the radially inner element ( 12 ) is coupled. Nozzle head according to one of the preceding claims, characterized in that the ring nut ( 9 ; 9 ' ) at least partially with the radially outer element ( 13 ) is coupled.

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